Where can I find detailed Cutody Law online?

For instance, if a non custodial parent was denied a Motion to Reduce their Child Support payments by a Judge in Maryland, where could that parent go online and find out details on how to file and exception (appeal) to that ruling? Detailed info, please. Basically, a law book online.

If not, I can always go to a law library I guess… lol

Sorry, it was supposed to read “how to file an exception (appeal) to that ruling”